The partnership with Twitter has it working with Microsoft to optimise how Bing crawls and indexes 'tweets'. Microsoft in turn will apply search algorithms to the Twitter messages, so that Bing users will not only be able to see a real-time feed of 'tweets' but also rank them by how relevant they are to their query, Yusuf Mehdi, senior vice president of Microsoft's Online Audience Business, said.

"This is a big deal we've been working on for a long time," Mehdi said.

To rank 'tweets' by relevance, a feature Microsoft calls Best Match, Bing will take into consideration a number of factors, such as who are the authors of the messages based on a 'social relevance' score Bing will assign to them, Mehdi said.

Bing will also evaluate the message's quality, noticing, for example, if it contains a link to an online article or web page. It will also take into consideration how popular the message is by calculating how many times it has been 're-tweeted' by others.

In addition to providing links to Twitter messages, Bing will extract the URLs of the pages that the messages are making reference to, so that users can go directly to that source of the information.

When providing links to 'tweets' that contain a shortened URL, Bing will put in parenthesis the main web domain of the link, so that users know, before clicking, whether it's a reputable site and thus avoid landing in a malicious phishing or malware-laden site.

Bing will also display a tag cloud of the most popular Twitter topics, so that users can click on and dive deeper into them.

The Twitter deal is nonexclusive, and hours later rival Google announced its own agreement with Twitter.

"In the past few years, an entirely new type of data has emerged, real-time updates like those on Twitter have appeared not only as a way for people to communicate their thoughts and feelings, but also as an interesting source of data about what is happening right now in regard to a particular topic," said Marissa Mayer, Google's vice president of search products and user experience.

"We believe that our search results and user experience will greatly benefit from the inclusion of this up-to-the-minute data, and we look forward to having a product that showcases how tweets can make search better in the coming months."

Still, it seems Bing is for now ahead of Google with an optimised search experience for Twitter that is already live.

Although Google remains by far the most popular search engine, Microsoft is making a big push to improve its position in this market, starting with Bing's launch in May and the broad search deal with Yahoo, which is awaiting regulatory approval.

"We're super happy with the Twitter partnership," said Qi Lu, president of Microsoft's Online Services Division. Lu declined to disclose financial details of the deal. He also said he wasn't sure on its duration.

Neither Mehdi nor Lu said much about the Facebook arrangement, other than to indicate that it will be similar in nature to Twitter's but that it will be implemented at a later date.

It will be interesting to see what shape the Facebook agreement takes, considering that Facebook allows individual members to make only basic profile information available via search engine results. Facebook has indicated it may let members make their profiles open to anyone on the web, including their status updates, but that hasn't happened yet.

Twitter, on the other hand, is a much more open service and most of its users make public their 'tweets', messages that can't be longer than 140 characters.

Facebook expects its deal with Bing to become active early next year, a Facebook spokeswoman said. Before Bing can make Facebook status updates searchable, Facebook has to first roll out to all users its new Publisher Privacy Control system, which is now being tested with a small group of users, the spokeswoman said.

"As you may recall, the new Publisher Privacy Control enables users to define who can see the content they publish on a per-post basis. For example, they may want to make some posts available to everyone, while restricting others to their friends and family," she said.

Microsoft and Facebook have an existing partnership through which Microsoft provides web search and search ads to Facebook.